Developing and validating a toolkit for cell type specific gene manipulation PIs: Clandinin and Shah Neurons express complex arrays of genes that play crucial roles in determining neuronal function. As such, single-gene mutations can lead to neurodevelopmental, neurophysiological, and neurodegenerative diseases. However, the nervous system is made up of many different types of neurons, which differ both in the genes they express and the function those genes perform. The ability to inactivate targeted genes only in the cell type of interest is therefore critical for our understanding of neural circuit function This application will generate a generalizable, validated set of transgenic flies and mice for cell type specifically manipulating genes that control the inputs, outputs, and activity patterns of neurons in physiological and behavioral studies of a wide array of circuits. This application describes three goals for developing and validating this toolkit. First, we will generate conditional allelesof 24 genes important for neuronal excitability and signaling in Drosophila. Second, we will validate our cell type specific gene disruption in vivo using a combination of voltage imaging, calcium imaging and behavioral assays, providing strong evidence of the broad utility of this toolkit. Third, since mice are critical model organisms for studying vertebrate nervous systems in health and in disease, we will adapt the same tool we use in flies to mice, targeting a key set of genes controlling excitation, inhibition and neuromodulation. Development of this toolkit will provide th neuroscience community with the means to manipulate essential neural genes with unprecedented precision in cell types of interest, thereby allowing fundamental questions about how genes shape neuronal circuit function to be addressed. As mutations in these classes of genes lead to devastating neurological disorders, this tool will facilitate studies that expand our understanding of these diseases and the treatment possibilities. As pharmacological approaches to treating brain dysfunction are ultimately limited by molecular specificity, understanding cell-type specific gene function is critical to the development of new treatment strategies. Finally, as the tool we will develop can be generalized to virtually any gene, future studies can extend the use of this tool to any gene of interest, in either flies or mice.